Water-based inks are preferred for ink-jet printing. However, water-soluble dyes when printed via ink-jet have poor waterfastness. To overcome the problems caused by the lack of waterfastness, some dyes have been made with carboxylate solubilizing groups attached to the dye molecule. These dyes, upon natural neutralization, change to the less soluble carboxylic acid form. Such dyes give greatly improved waterfastness, but still are not totally waterfast. Further, inks with such dyes are limited to printing on porous substrates such as paper, and perform poorly on such substrates as packaging materials. Water-soluble dyes, when printed on non-absorbable surfaces, remain wet and somewhat hygroscopic and can be smeared by simple abrasion.
A need remains to provide a water-soluble dye for ink-jet printing evidencing substantially total waterfastness. The present invention provides a polar, water-soluble dye which undergoes a change on the surface of the print substrate, changing the dye to a hydrophobic, water-insoluble polymeric dye.